#include <stdio.h>


int main()
{
    long int a[50] = {0};
    //第50个月有多少兔子

    a[0] = 1;
    a[1] = 1;
    for(int i = 2;i < 50;i++)
    {
        a[i] = a[i - 2] + a[i - 1]; 
    }
    printf("%ld\n",a[49]);
    return 0;
}